1. Field of the Invention
The present invention relates to a method of measuring the state of displacement of tracks recorded on a magnetic tape.
2. Description of the Prior Art
It is recently an important subject to narrow the track width as the high density recording of magnetic tape is being promoted. The improvement of the track linearity becomes more important as the track width becomes narrower. This is because of the fact that as the track is deformed, a track adjacent to the desired track is traced, or the head does not trace the desired track correctly and the reproduced signal deteriorates. It is therefore an essential matter to understand the displacement state of the track for achieving high density recording.
The conventional method of measuring track displacement was to develop and visualize the track recorded obliquely relative to the longitudinal direction of the magnetic tape by using magnetic fluid, read the track position along a line perpendicular to the longitudinal direction of the magnetic tape, and evaluate the linearity of the track by comparing between a read position and a reference position without deformation of the track (e.g. Japanese Laid-open Patent No. 62-172505).
In such a conventional method and composition, however, since the track displacement amount generally differs at different positions in the longitudinal direction of the magnetic tape, the data varies when several points on the magnetic tape are measured, so that an accurate evaluation is difficult. Besides, since position data read from several tracks are assumed equivalent to position data of one track, the obtained track deformation amount is an average with respect to time, so that the changes of the track linearity with respect to time cannot be detected.